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3. Language Fundamentals:

This chapter introduces types and variables to meet the following objectives:

Value Types
Reference Types
Namespace
Conversions
Expressions and Statements

Types

C# .NET proviides a base set of data types known as Common Type System (CTS). The CTS grouped as

(1) Value Types and (2) Reference Types.

1. Value Types

Value types are variables that contain their data stored in an area of memory called the stack. C# provides three kinds of Value types, they are
1. Primitive Data types (Simple types) or Built-in types
2. Struct types or Uder defined typesand
3. Enumeration Types.

2. Reference Types

Reference type stores the address on the Stack and the objects (data) on the Heap.
Reference types are Object, Class, Interface, Delegagte, String and Array.

1.Object: The Object type is the most general type in the Framework. You can convert any type to System.Object. System.Object has four member methods. ToString, GetType, and Equals members inherited from this type.

2.Class: Class is a template or blue print used to create multiple objects with similar features.

3.Interface: Interfaces are also known as contracts., The classes must implement the interface members.

4.Delegate: A delegate is a pointer to a method. Delegate like a class that can hold a reference to a method.

5.String: Strings are immutable in .Net. Immutable means any change to a string causes the runtime to create a new string and allocates new object in memory.

S = “Welcome ”;
S += “to ”;
S += “C# “;
S += “World!”;

6.Array: An Array is a collection of objects and they are stored on heap.

Array Declaration
int [] iArray;
iArray = new int[100];

A namespace is a group of related hierarchical classes. The Advantage of using namespaces is, to avoid conflicts when you have multiple classes with the same name. eg:

using System;
using System.Collections.Geeneric;

Conversions

Conversions can be categorized into Implicit Coonverrsionn, Explicit Conversion, Boxing, and Unboxing.

Implicit Conversion:
int i =5;
double d = i;

Explict Conversion
double d =100.34;
int i = (int) d;

Boxing and Unboxing is done between Value types and Reference Types

Boxing

Boxing: Converting value type to an Object type is known as Boxing.
int i =99;
object o = i;

Unboxing

Unboxing : Converting Object type to value type is known as Unboxing.
object o = 98.5;
int i = (int) o;

Expressions and Statements

        Expression Types 
        Arithmetic Operator are categorized into Binnary Operator and Unary Operators.
        Binary Operator		Meaning
        +	                Addition
        -	                Subtraction
        *	                Multiplication
        /	                Division
        %	                Modulus
        Unary Operator	        Meaning
        ++	                Incrementing  (++i prefix and i++ postifx increemnts)
        --	                Decrementing  (--i prefix and i-- postifx decreemnts)
        Assignment operators assign a value to a variable using the follwinng symbols.
        Assignment Operators    Meaning
        =                       Assigning
        +=                      Addition
        -=                      Subtraction
        *=                      Multiplication
        /=                      Division
        %=                      Modulus
        &=                      AND
        |=                      OR
        ^=                      Exclusive OR
        <<=                     Left Shift
        >>=                     Right Shift
        A Relational Operator basically takes two values and evaluates the 
        relationship between them.  The operator returns a Boolean value.
        Relational Operators    Meaning
        ==                      Equal to
        !=                      Not equal
        <                       Less than
        >                       Greater than
        <=                      Less than or equal to
        >=                      Greater than or equal to  
        Local Operators are used exclusively with Boolean values.  
        Logical Operators       Meaning
        &&                      AND
        ||                      OR
        !                       NOT
        Bitwise Operators
        Bitwise  Operators basically return a Boolean value after the operation 
        has been performed.
        Bitwise Operators       Meaning
        !                       NOT
        &                       Bitwise AND
        |                       Bitwise  OR
        Ternary Operators 
        Ternary is also known as a conditional operator.  
        Eg:   expression1 ? expression2 : expression2
        

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